1. Field of the Invention
The present invention relates to a current sensor for measuring the magnitude of an electric current, and relates to, for example, a current sensor including a magnetoresistance effect element (a TMR element or a GMR element).
2. Description of the Related Art
In the past, in a field such as a technology for driving motors in electric vehicles, hybrid vehicles, and the like, a current sensor has been desired that is capable of measuring the driving current of a motor in a non-contact manner. As such a current sensor, a current sensor has been proposed that uses a magnetoresistance effect element outputting an output signal owing to an induction magnetic field from a current to be measured. Such a technique has been disclosed in, for example, U.S. Pat. No. 6,387,458.
A current sensor disclosed in U.S. Pat. No. 6,387,458 includes a GMR element, as the magnetoresistance effect element. The basic film configuration of the GMR element includes an antiferromagnetic layer, a ferromagnetic fixed layer, a non-magnetic material layer, and a free magnetic layer. The ferromagnetic fixed layer is formed on the antiferromagnetic layer so as to be in contact therewith, and owing to an exchange coupling magnetic field (Hex) occurring between the ferromagnetic fixed layer and the antiferromagnetic layer, the magnetization direction of the ferromagnetic fixed layer is fixed in one direction. The free magnetic layer is laminated with the non-magnetic material layer (non-magnetic intermediate layer) sandwiched between the free magnetic layer and the ferromagnetic fixed layer, and the magnetization direction of the free magnetic layer is changed owing to an external magnetic field. In the current sensor including the GMR element, the current value of a current to be measured is detected using the electrical resistance value of the GMR element, which fluctuates owing to a relationship between the magnetization direction of the free magnetic layer, which changes owing to the application of an induction magnetic field from the current to be measured, and the magnetization direction of the ferromagnetic fixed layer.